The present invention generally relates to a cylinder block for an internal combustion engine and more particularly relates to a cylinder block with enhanced structural stiffness.
Deflection of a cylinder block of an engine is generally undesirable. Such deflection contributes to undesirable vibrational modes and noise emission levels when an assembled engine is running. It is known to provide stiffened block components in order to generally reduce the level of noise emitted from a running engine. For example, stiffened cylinder block walls are disclosed in U.S. Pat. Nos. 4,470,376; 4,461,247; and 4,627,394.
Block deflection can also lead to manufacturing complications. A conventional cylinder block substantially deflects between a free condition and an assembled condition due to the loads and stresses from cylinder head bolts and other components. Such distortion leads to an improper fit of components and unwanted tolerance changes. Accordingly, simulated loads are applied to conventional cylinder blocks during machining operations. An example of such a process is known as torque plate honing, whereby a torque plate is bolted to the conventional block to approximate the loads of a bolted-on cylinder head during honing of the cylinder bores. The bores are thus round when the cylinder head is later mounted to the block. Torque plate honing is necessitated by the degree of deflection of a conventional block. Otherwise, if the cylinder bores were machined while the block was in an unloaded condition, the cylinder bores would deflect from a round shape when the block is in its loaded, assembled condition, resulting in imprecise tolerances, undesirable wear patterns and poor oil consumption. Unfortunately, torque plate honing is costly and difficult to control in a production environment.
Conventional cylinder blocks have various openings formed therein to permit the connection of conduits, hoses, and other components. For example, an opening is conventionally formed in the wall of a cylinder block to accommodate the mounting of an oil cooler in fluid communication with the water jacket. A lack of structural material in such an opening leads to undesirable flexibility of the block. Accordingly, a need exists to design such a cavity with improved stiffness.
Another component known to emit noise is a cover plate that is bolted to a side of the cylinder block to cover reciprocating pushrods that extend from the crankcase to the cylinder head. The cover plate is known to transmit substantial levels of noise.
Accordingly, design features are desirable which provide a stiff block structure in order to reduce noise emission levels and to reduce deflection between free and assembly-loaded conditions.